WASHINGTON - The Bush administration and the nation's intelligence agencies are blocking the release of sensitive information about the Sept. 11 terrorist attacks on the World Trade Center and the Pentagon, delaying publication of a 900-page congressional report on how the terrorist assault happened.

Intelligence officials insist the information must be kept secret for national security reasons. But some of the information is already broadly available on the Internet or has been revealed in interim reports on the investigation, leading to charges that the administration is simply trying to avoid enshrining embarrassing details in the report.

Disputed information includes a well publicized warning from an FBI agent that al-Qaida supporters might be training in U.S. flight schools and the names of the president and his national security adviser as people who may have received warnings that a terrorist attack was possible before Sept. 11, one official said.

"We're trying to keep in this report some matters that have been talked about in public, discussed in newspapers, and not to do that, flies in the face of common sense," Rep. Porter Goss, chairman of the House Intelligence Committee, said Monday.

"The White House is continuing a trend of presenting obstacles to us rather than cooperating with us," said Tim Roemer, a former House member who participated in the congressional inquiry and is now a member of the independent commission investigating Sept. 11.

Goss, a Florida Republican, and Sen. Bob Graham, a Florida Democrat who headed the Senate Intelligence Committee last year, co-chaired a joint investigation over 10 months that detailed security lapses, bad communication and missed clues by the CIA and FBI that preceded the Sept. 11 attacks.

In December, the joint inquiry produced a summary of findings and recommendations on how to improve intelligence, but the complete report was withheld so agencies could review and declassify some portions of it.

Graham, who will officially announce his presidential campaign Tuesday, has said he thinks much of the delay is because agencies and the administration want to avoid embarrassment, not for valid national security reasons.

Goss, Graham and staff director Eleanor Hill had hoped to release the final report by February or March. Now they are hoping to release it Memorial Day, Goss said.

"I'm very frustrated this has taken this long," said Goss, a retired CIA officer with close ties to the administration. "There's a tendency for every executive to keep matters closed up, but most of what's in dispute should be made public."

Hill said she could not discuss the specifics of the information in dispute, but said a working group of intelligence officials objected to including some testimony from public hearings last fall and some data in her interim reports.

"Maybe they didn't realize it had already been made public, but we see no reason to keep it out of the report," said Hill, a former Pentagon inspector general.

An intelligence official familiar with the review process said on condition of anonymity Monday that "the process has taken time because many portions of the report need to remain classified to protect sources and methods."

The official would not comment on specific issues in the report, and said "we hope to complete the process by the end of this month."

But an official familiar with the report said one topic of disagreement was the so-called Phoenix memo of July 2001, in which an FBI agent warned his supervisors that Osama bin Laden's followers might be enrolling in U.S. flight schools.

The joint inquiry, in a Sept. 24 staff report, included portions of the memo and summarized how it was handled and ignored by FBI officials. Most of the memo is on several Internet sites. Now intelligence officials want to block releasing excerpts of the memo.

Sen. Richard Shelby of Alabama, the ranking Republican on the Senate committee during the investigation, said: "The memo should be declassified except for portions that might compromise an ongoing investigation."

The Bush administration also consistently have fought identifying top officials, including the president and national security adviser Condoleezza Rice, who may have received warnings in 2001 that bin Laden's network planned to hijack commercial aircraft.

As a result, the report includes vague references to "senior administration officials."

"We fought that argument (to name officials) and lost," said Goss. "There's a history in these types of reports, going back many presidencies, that you do not mention the president of the United States, period."

Goss said there was "no cover-up of vital information" and predicted the final report will include some embarrassing details but "no 'gotcha' material about any administration."

Roemer, an Indiana Democrat, said he sees a pattern of "overclassification" by an administration unwilling to disclose information and agencies that reflexively fight disclosure.